The PHQ-9 (PHQ-D in some sources) is the 9-question depression scale from the Patient Health Questionnaire (PHQ). The results of the PHQ-9 may be used to make a depression diagnosis according to DSM-IV criteria. (see: Wikipedia)
scoring_phq9(data, items = 1:9, keep = TRUE, nvalid = 6, digits = NULL)
A character vector with the PHQ-9 item names ordered from 1 to 9,
or a numeric vector indicating the column numbers of the PHQ-9 items in
Logical, whether to keep the single items and whether to return variables containing the number of non-missing items on each scale for each respondent. The default is TRUE.
A numeric value indicating the number of non-missing items required for score calculations. The default is 7.
Integer of length one: value to round to. No rounding by default.
The function returns 3 variables:
nvalid.phq9: Number of valid values (MAX=9)
score.phq9: PHQ-9 score
cutoff.phq9: PHQ-9 as categorical variable
Number of items: 9
Item range: 0 to 3
Reverse items: none
Score range: 0 to 27
< 5 = "minimal";
5 to 9 = "mild";
10 to 15 = "moderate";
15 to 19 = "moderately severe",
\(\ge\) 20 = "severe"
Minimal clinically important difference: none
Treatment of missing values: Questionnaires with up to two missing values are scored,
replacing any missing values with the average score of the completed items. (Arrietta et al. 2017)
Arrieta et al. (2017) (https://doi.org/10.1002/jclp.22390)
Kroenke et al. (2010) (https://doi.org/10.1016/j.genhosppsych.2010.03.006)